Photoelectric conversion device and method of production thereof

ABSTRACT

A photoelectric conversion device comprising at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, wherein either one of the charge transfer layers comprises a semiconductor acicular crystal layer comprising an aggregate of acicular crystals or a mixture of an acicular crystal and another crystal, and a method of producing the device are disclosed. Consequently, a photoelectric conversion device being capable of smoothly carrying out transfer of electrons and having high photoelectric conversion efficiency is provided.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The prevent invention relates to a photoelectric conversiondevice and a method of producing the device, and more particularly, to aphotoelectric conversion device comprising at least an electronacceptive charge transfer layer, an electron donative charge transferlayer, and a light absorption layer formed between these charge transferlayers and a method of producing the device.

[0003] 2. Related Background Art

[0004] A solar cell utilizing semiconductor junction of silicon, galliumarsenide or the like is generally known as a method of converting lightenergy into electric energy. Among them, a crystal silicon solar celland a polycrystalline silicon solar cell utilizing a p-n junction of asemiconductor and an amorphous silicon solar cell utilizing a p-i-njunction of a semiconductor have been developed for practicalapplication. However, since the production cost of a silicon solar cellis relatively high and much energy is consumed in the productionprocess, it is required to use a solar cell for a long duration in orderto compensate the production cost and the consumed energy. Especially,the high production cost interferes with the wide use of the solar cell.

[0005] On the other hand, recently, solar cells using CdTe andCuIn(Ga)Se have been studies for practical application as secondgeneration thin film solar cells, and regarding the solar cells usingthese materials, problems in environmental pollution and resources arepointed out.

[0006] Besides those dry type solar cells using the semiconductorjunction, there is also suggested a wet type solar cell utilizing aphotoelectric chemical reaction caused in the interface of asemiconductor and an electrolytic solution. A metal oxide semiconductorsuch as titanium oxide, tin oxide, or the likes to be used for the wetsolar cell has an advantage of lowering a solar-cell manufacturing costas compared with silicon, gallium arsenide, or the likes to be used forthe foregoing dry type solar cells. Above all, titanium oxide isexpected to be a future energy conversion material since it is excellentin both photoelectric conversion property in an ultraviolet region andstability. Since a stable semiconductor such as titanium oxide, however,has a wide band gap not less than 3 eV, only ultraviolet rays, which areabout 4% of sunrays, can be utilized and the photoelectric conversionefficiency has been insufficient.

[0007] For that, a photochemical cell (dye-sensitized wet type solarcell) comprising an photoelectric semiconductor adsorbing dye on thesurface has been studied. At the beginning, a single crystal electrodeof a semiconductor was used for such a photochemical cell. Examples ofthe electrode are titanium oxide, zinc oxide, cadmium sulfide, tinoxide, or the like. Since an amount of the coloring agent to be adsorbedon the single crystal electrode was, however, low to lower photoelectricconversion efficiency and the cost was high, a porous semiconductorelectrode was tried to be used. Tubomura et al. reported (NATURE,261(1976) p. 402) that the photoelectric conversion efficiency had beenimproved by adsorbing dye in a semiconductor electrode made of a porouszinc oxide produced by sintering a fine particle. Proposals of employingporous semiconductor electrodes were also made in Japanese PatentApplication Laid-Open No. 10-112337 and Japanese Patent ApplicationLaid-Open No. 9-237641.

[0008] Graetzel et al. also reported (J. Am. Chem. Soc. 115(1993) 6382,U.S. Pat. No. 5,350,644) that performance as high as that of a siliconsolar cell was achieved by improving dye and a semiconductor electrode.There, a ruthenium type coloring agent was used as dye and an anatasetype porous titanium oxide (TiO₂) was used as a semiconductor electrode.

[0009]FIG. 6 is a schematic cross-sectional view of a photochemical cellusing dye-sensitized semiconductor electrode reported by Graetzel et al.(hereafter called as Graetzel type cell in this description) to show anoutline structure and functions of the cell.

[0010] In FIG. 6, 14a, 14 b denote a glass substrate, 15 a, 15 b denotea transparent electrode formed on a glass substrate, and 61 denotes ananatase type porous titanium oxide semiconductor layer composed of finetitanium oxide particles bonded to one another in porous state. Further,62 denotes a light absorption layer of dye bonded to the surface of thefine titanium oxide particles and 63 denotes an electron donativeelectrolytic solution and, for example, an electrolytic solutioncontaining iodine ions may be employed as the electron donativeelectrolytic solution.

[0011] A method of manufacturing Graetzel type cell will be describedbelow.

[0012] At first, a layer of an anatase type titanium oxide fine particleis formed on a glass substrate 14 a on which a transparent electrode 15a is formed. A various kinds of formation methods are available, andgenerally, formation of an approximately 10 μm thick semiconductor layer61 of an anatase type titanium oxide fine particle is carried out byapplying a paste containing dispersed anatase type titanium oxide fineparticles with 10 to 20 μm particle diameter to a transparent electrode15 a and then firing the paste at 350 to 500° C. Such a method canprovide a layer with about 50% porosity and about 1000 roughness factor(practical surface area/apparent surface area) and in which the fineparticles are well bonded to one another.

[0013] After that, dye is adsorbed in the produced titanium oxide layer61. Various kinds of substances are studied to be used as dye andgenerally a Ru complex is utilized. The titanium oxide layer 61 isimmersed in a solution containing dye and dried to bind the coloringagent to the surfaces of the titanium oxide fine particles and to form alight absorption layer 62. A substance which does not inhibit adsorptionof dye in a titanium oxide layer and is capable of dissolving dye welland electrochemically inert even if remaining on the surface of theelectrode (the transparent electrode and the titanium oxide) is suitableas a solvent to dissolve the coloring agent, and from that point,ethanol and acetonitrile are preferably used.

[0014] Further, as a opposed electrode, a glass substrate 14 b on whicha transparent electrode 15 b is formed is made ready and an ultra thinfilm of platinum or graphite is formed on the surface of the transparentelectrode 15 b. The ultra thin film works as a catalyst at the time oftransporting electric charge to and from an electrolytic solution 63.

[0015] After that, while the transparent electrode 15 a, 15 b being setin the inner sides, the glass substrates 14 a, 14 b are overlaid as tohold the electrolytic solution 63 between them to give a Graetzel typecell. Acetonitrile, propylene carbonate, or the likes which areelectrochemically inert and capable of dissolving a sufficient amount ofan electrolytic substance are preferably used as a solvent for theelectrolytic solution 63. As an electrolytic substance, a stable redoxpair such as I⁻/I₃ ⁻, Br⁻/Br₃ ⁻ is preferably used. At the time offorming, for example, a pair of I⁻/I₃ ⁻, a mixture of iodine ammoniumsalt and iodine is used as a solute of the electrolytic solution 63.

[0016] Finally, it is preferable to seal the obtained cell with anadhesive to provide durability.

[0017] Next, the action principle of the Graetzel type cell will bedescribed below. Light is radiated to the Graetzel type cell from theleft side shown in FIG. 6. Subsequently, electrons of the coloring agentconstituting the light absorption layer 62 are excited owing to theincident light and the excited electrons are efficiently injected to thetitanium oxide layer 61 and transferred to a conduction band of titaniumoxide. The coloring agent which loses electrons and falls into oxidizedstate is quickly reduced by receiving electrons from iodine ion in theelectrolytic solution 63 and turns back to the original state. Theelectrons injected into the titanium oxide layer 61 are moved owing to amechanism of such as hopping conduction among the titanium oxide fineparticles and reach the anode 15 a (the left side transparent electrodein figure). On the other hand, the iodine ions which are in oxidizedstate (I₃ ⁻) by supplying electrons to the coloring agent are reduced byreceiving electrons from the cathode (the right side transparentelectrode in figure) 15 b and turn back to the original state (I⁻).

[0018] As is suggested by such an action principle, in order toefficiently separate the electrons and the holes generated in thecoloring agent and move them, the energy level of the electrons of thecoloring agent in the excited state has to be higher than that of theconduction band of titanium oxide, and the energy level of the holes ofthe coloring agent has to be lower than the redox level of iodine ion.

[0019] Further improvements on the photoelectric conversion efficiency,the short circuit current, the open circuit voltage, the filter factor,and durability are desirable to promote replacement of a silicon solarcell with such a Graetzel type cell.

[0020] However, since the foregoing coloring agent-sensitizedsemiconductor electrode is a titanium oxide film produced by applyingthe solution containing dispersed titanium oxide fine particles to thetransparent conductive film (the transparent electrode) 15 a andsintering at high temperature after drying, the excited electrons tendto be scattered in the interfaces of the transparent electrode and thetitanium oxide fine particles and in the interfaces of titanium oxidefine particles themselves. The internal resistance generated in theinterfaces of the transparent electrode and the titanium oxide fineparticles and in the interfaces of titanium oxide fine particlesthemselves, therefore, is increased to result in a decrease inphotoelectric conversion efficiency. Moreover, movement of the excitedelectrons to the redox system or the like in the interfaces of thetitanium oxide fine particles themselves also causes decease of thephotoelectric conversion efficiency.

[0021] Further, since the foregoing coloring agent-sensitizedsemiconductor electrode comprises a sintered body of titanium oxide fineparticles, there are caused problems that it takes a long time to adsorbdye in the titanium oxide fine particles in the periphery of thetransparent electrode and that it is slow to diffuse ions in theelectrolytic solution 63.

Summary Of The Invention

[0022] An object of the present invention is, therefore, to provide aphotoelectric conversion device capable of smoothly supplying andreceiving electrons and having high photoelectric conversion efficiency.

[0023] Another object of the present invention is to provide aphotoelectric conversion device comprising a semiconductor electrode inwhich electrons, holes, and ions in a light absorption layer containingdye and a charge transfer layer containing an electrolytic solutionmoves best and thus the light absorption layer and the charge transferlayer have excellent diffusion properties during production.

[0024] The other object of the present invention is to provide a methodof producing a photoelectric conversion device having suchcharacteristics.

[0025] The present invention, therefore, provides a photoelectricconversion device comprising at least an electron acceptive chargetransfer layer, an electron donative charge transfer layer, and a lightabsorption layer existing between the charge transfer layers, whereineither one of the charge transfer layers is a semiconductor acicular (orneedle) crystal layer comprising aggregate of acicular crystals.

[0026] The present invention further provides a method of producing aphotoelectric conversion device which comprises at least an electronacceptive charge transfer layer, an electron donative charge transferlayer, and a light absorption layer existing between the charge transferlayers, the method comprising applying a solution containing acicularcrystals on a substrate and firing the substrate to form a semiconductoracicular crystal layer comprising aggregate of acicular crystal on thesubstrate and utilizing the semiconductor acicular crystal layer aseither one of the charge transfer layers.

[0027] The present invention further provides a method of producing aphotoelectric conversion device which comprises at least an electronacceptive charge transfer layer, an electron donative charge transferlayer, and a light absorption layer existing between the charge transferlayers, the method comprising forming a semiconductor acicular crystallayer comprising aggregate of acicular crystals on a substrate by a CVDprocess and utilizing the semiconductor acicular crystal layer as eitherone of the charge transfer layers.

[0028] Moreover, a photoelectric conversion device comprising at leastan electron acceptive charge transfer layer, an electron donative chargetransfer layer, and a light absorption layer existing between the chargetransfer layers, wherein either one of the charge transfer layers is asemiconductor layer comprising a mixture with two or more kinds ofdifferent morphologies (or configurations) or compositions and at leastone of the kinds of the semiconductor layer is an acicular crystal.

[0029] The method of producing a photoelectric conversion device of thepresent invention is a method of producing a photoelectric conversiondevice which comprises at least an electron acceptive charge transferlayer, an electron donative charge transfer layer, and a lightabsorption layer existing between the charge transfer layers, the methodcomprising applying a semiconductor mixture solution comprising asemiconductor mixture with two or more kinds of different morphologiesor compositions on a substrate and firing the substrate to form asemiconductor mixed crystal layer on the substrate, and utilizing thesemiconductor mixed crystal layer as either one of the charge transferlayers.

[0030] The method of producing photoelectric conversion device of thepresent invention is a method of producing a photoelectric conversiondevice which comprises at least an electron acceptive charge transferlayer, an electron donative charge transfer layer, and a lightabsorption layer existing between the charge transfer layers, the methodcomprising the steps of applying a solution containing a semiconductoracicular crystal on a substrate and firing the substrate to form anacicular semiconductor crystal layer, further depositing a singlesubstance or a mixture with a different morphology or composition fromthat of the acicular crystal to the semiconductor layer to form asemiconductor mixed crystal layer on the substrate, and utilizing thesemiconductor mixed crystal layer as either one of the charge transferlayers.

[0031] The method of producing the other photoelectric conversion deviceof the present invention is a method of producing a photoelectricconversion device which comprises at least an electron acceptive chargetransfer layer, an electron donative charge transfer layer, and a lightabsorption layer existing between the charge transfer layers, the methodcomprising the steps of growing an acicular crystal on a substrate,depositing to the acicular crystal a single substance or a mixture witha different morphology or composition from that of the acicular crystalto form a semiconductor mixed crystal layer on the substrate, andutilizing the semiconductor mixed crystal layer as either one of thecharge transfer layers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIGS. 1A, 1B, 1C and 1D are outline cross-sectional views showingphotoelectric conversion devices of the present invention;

[0033]FIGS. 2A, 2B and 2C are cross-sectional views illustrating theconstitution examples of light radiation, the transparent electrodes,and mixed crystal layers of the present invention;

[0034]FIGS. 3A, 3B, 3C and 3D are cross-sectional views illustrating thebonding state of the mixed crystal of the present invention;

[0035]FIGS. 4A, 4B, 4C and 4D are cross-sectional views illustrating themixed crystals from the nanny-holes of the present invention;

[0036]FIGS. 5A, 5B, 5C and 5D are cross-sectional views illustrating themixed crystals from the substrate of the present invention;

[0037]FIG. 6 is a cross-sectional view of a conventional example of aGraetzel type cell;

[0038]FIG. 7 is a simplified figure of an open-to-atmosphere type CVDapparatus;

[0039]FIGS. 8A, 8B and 8C illustrate the structure of an acicularcrystal;

[0040]FIGS. 9A and 9B are cross-sectional views illustrating a cellemploying an acicular crystal and a mixed crystal; and

[0041]FIGS. 10A, 10B and 10C are cross-sectional views illustrating thestate of a mixed crystal;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] The main characteristic of a photoelectric conversion device ofthe prevent invention is that an acicular crystal is used for anelectron acceptive (n-type) or an electron donative (p-type) chargetransfer layer. The acicular crystal means so-called whisker andpreferably includes a defect-free acicular single crystal and anacicular crystal containing screw dislocation. As illustrated in FIGS.8A, 8B and 8C, the acicular crystal in the present invention alsoincludes a crystal in the present invention also includes grown from onepoint as to form various shapes including a tetrapod-like shape (FIG.8A), a dendrite shape (FIG. 8B), and a broken line-like shape (FIG. 8C).

[0043] Further, the acicular crystal of the present invention includesthose with all kinds of shapes of such as cylindrical, conical, conicalwith truncated ends, cylindrical with sharpened tips or flat tips.Moreover, the acicular crystal includes thoses with a triangularpyramid, a rectangular pyramid, a hexagonal pyramid, and other polygonalpyramid shapes, their truncated shapes, a triangular prism, arectangular prism, a hexagonal prism, and other polygonal prism shapes,and sharpened tip-levelled ones and furthermore, the crystal includesthose with broken line structure of above described shapes.

[0044] Either one of charge transfer layers is a semiconductor layercontaining a mixture with two or more different morphologies or with twoor more different compositions and one or more of semiconductor layersare a mixed crystal containing an acicular crystal. Example ofmorphology of the mixed crystal are illustrated in FIGS. 10A, 10B and10C. Respectively FIG. 10A shows an acicular crystal bearing particlesin the surrounding: FIG. 10B shows an acicular crystal bearing anacicular substance in the surrounding: and FIG. 10C shows an acicularcrystal bearing a film-like substance in the surrounding.

[0045] In order to effectively explain the effects of an acicularcrystal and its mixed crystal, cells of the present invention will bedescribed while being compared with a conventional Graetzel type cell.

[0046]FIGS. 1C and 1D are outline cross-sectional views showingphotoelectric conversion devices of the present invention. In thesefigures, 10 denotes a substrate bearing an electrode, 11 b denotes anabsorption layer-modified semiconductor mixed crystal layer, 12 denotesa charge transfer layer, and 13 denotes a substrate bearing anelectrode. The substrate bearing an electrode 10 is, for example, aglass substrate 14 on which a transparent electrode layer 15 is formed,the absorption layer-modified semiconductor mixed crystal layer 11comprises a semiconductor acicular crystal 17 and a light absorptionlayer 16 formed on the surface of the crystal. The semiconductoracicular crystal 17 is used as one charge transfer layer and the lightabsorption layer 16 is formed between the charge transfer layer and theother charge transfer layer 12.

[0047] <Regarding the Constitution of an Photoelectric Conversion Deviceof the Present Invention>

[0048] In dye-sensitized type cell represented with the foregoingGraetzel type cell, since the light absorbency of one coloring agentlayer is insufficient, the surface area of the light absorption layer iswidened to increase the practical quantity of absorbed light. As amethod of increasing the surface area, a method of dispersing andbinding the fine particles just like in the foregoing Graetzel type cellmay be employed, but by the method, there occurs a problem that theelectron transfer efficiency is not sufficiently efficient. In theforegoing Graetzel type cell, for example, the photoelectric conversionefficiency is sometimes higher in the case where light incidence iscarried out from the side of the transparent electrode 15 a having thetitanium oxide semiconductor layer 61 than in the case where lightincidence is carried out from the opposite electrode 15 a side. That isnot only means the difference of the quantity of the light by absorbanceby the coloring agent but also suggests that the possibility ofelectrons excited by the light absorbance to move the titanium oxidesemiconductor layer 61 and to reach the transparent electrode 15 a tendto be decreased more as the distance of the light excitation position tothe transparent electrode becomes wider. In other words, it can besuggested that electrons are not sufficiently moved in the Graetzel typecell having many crystal grain boundaries.

[0049] An example of photoelectric conversion devices of the presentinvention will be described with reference to FIGS. 1A to 1D and FIGS.2A to 2C.

[0050]FIG. 1A is an outline cross-sectional view showing an example ofthe photoelectric conversion devices of the present invention. In thefigure, 10, 13 denote substrates bearing electrodes, 11 a denotes asemiconductor acicular crystal layer having a light absorption layer onthe surface (absorption layer-modified semiconductor acicular crystallayer), and 12 denotes a charge transfer layer. FIG. 1B is a partlyenlarged cross-sectional view of the cross-sectional view of FIG. 1A andin the figure, 14 denotes a glass substrate and 15 denotes a transparentelectrode and they are equivalent to the substrate 10 bearing anelectrode of FIG. 1A. Further, 16 denotes a light absorption layer and17 denotes a semiconductor acicular crystal and they are equivalent tothe light absorption layer-modified semiconductor acicular crystal layer11 a.

[0051]FIGS. 1C and 1D are outline cross-sectional views showing otherexamples of the photoelectric conversion devices of the presentinvention. In those figures, 10 denotes a substrate bearing anelectrode, 11 b denotes an absorption layer-modified semiconductor mixedcrystal layer, 12 denotes a charge transfer layer, and 13 denote asubstrate bearing an electrode. The substrate 10 bearing an electrodeis, for example, a glass substrate 14 on which a transparent electrodelayer 15 is formed, the absorption layer-modified semiconductor mixedcrystal layer 11 comprises and a semiconductor acicular crystal 17 and alight absorption layer 16 formed on the surface. The semiconductoracicular crystal 17 works as one of charge transfer layers and thus thelight absorption layer 16 is to be positioned between this chargetransfer layer and the other charge transfer layer 12.

[0052] As compared with a fine particle crystal layer, the mixed crystallayer of the present invention has low possibility of scattering ofelectrons or holes generated by photoexcitation by grain boundariesuntil the electrons or holes reach a current collector. Especially, asshown in FIG. 1D, in the case where the mixed crystal layer is so formedas to join one ends of all of acicular crystals to an electrode and asto bond different types of micro crystals to the acicular crystals bysintering, the effects of grain boundaries on movement of electrons orholes are almost completely eliminated as compared with a case of aGraetzel type cell.

[0053] A photoelectric conversion device of the present inventionpreferably comprises an acicular crystal or a mixed crystal for ann-type wide gap semiconductor or a p-type wide gap semiconductor. In thecase where the acicular crystal or a mixed crystal is an n-type wide gapsemiconductor, a p-type wide gap semiconductor or an electron donativecharge transfer layer 12 of an electrolytic solution containing a redoxpair or of a conductive polymer is required to be on the opposite to then-type wide gap semiconductor while sandwiching a light absorption layer(containing, for example, dye) 16. On the other hand, in the case wherethe acicular crystal or a mixed crystal is a p-type wide gapsemiconductor, an electron acceptive charge transfer layer 12 isrequired to be on the opposite to the p-type wide gap semiconductorwhile sandwiching a light absorption layer 16.

[0054] In the case where either one of the substrates 10, 13 bearingelectrodes is set to be a light incident plane, the electrode and thesubstrate have to be transparent at least in the light incident side.FIGS. 2A, 2B and 2C are outline cross-sectional views illustratingpractical examples of photoelectric conversion devices of the presentinvention and in the figures, 21 denotes a glass substrate bearing atransparent electrode and 22 denotes an electrode having notransmissivity (or a substrate bearing an electrode having notransmissivity). In the constitution illustrated in FIG. 2A, the glasssubstrate 21 bearing an electrode is formed in the side of theabsorption layer-modified semiconductor acicular crystal layer 11 (theabsorption layer-modified semiconductor mixed crystal layer in theconstitutions illustrated in FIGS. 1C and 1D) to carry out lightincidence from the left side of the figures. To the contrary, in theconstitution illustrated in FIG. 2B, the glass substrate 21 bearing atransparent electrode is installed in the charge transfer layer 12 sideto carry out light incidence from the right side of the figure. As longas the absorption or reflection of incident light to the lightabsorption layer 16 can be negligible, any constitution is applicable.Further, as illustrated in FIG. 2C, the constitution may be constitutedas to use the glass substrate 21 bearing a transparent electrode forboth sides and as to carry out light incidence from any side.

[0055] The constitution may optionally be selected among the exemplifiedconstitutions in accordance with the formation method of thesemiconductor crystal layer 11, the formation method and the compositionof the charge transfer layer 12, and so forth. In the case where, forexample, the acicular crystal layer is formed by oxidizing a metalsubstrate, the acicular crystal side is inevitably used as the electrodewith no light transmissivity. On the other hand, in the case where theacicular crystal layer is formed by firing an acicular crystal powder,the acicular crystal side can be employed as the glass substrate bearinga transparent electrode, for the acicular crystal layer can be formed ata relatively low temperature and the transparent electrode is scarcelydeteriorated during the acicular crystal formation process.

[0056]FIGS. 9A and 9B are figures illustrating practical constitutionsof the foregoing acicular crystal and mixed crystal. As compared withthe Graetzel type cell shown in FIG. 6, the effects of grain boundariesare almost completely eliminated, so that electrons and holes can easilybe moved. Further, as shown in FIG. 9B, a semiconductor crystal 18 isadsorbed in the acicular crystal 17, so that the effects of the grainboundaries can be suppressed and roughness factor can be improved and,moreover, the radiated light can reach a wide range of areas even iflight is radiated to any plane. A large number of electrons are,therefore, enabled to move to obtain a cell of a photoelectricconversion device with high conversion efficiency.

[0057] The mixed crystal to be employed for the present invention willbe described below.

[0058] <Regarding an Acicular Crystal and a Mixed Crystal>

[0059] In the case of a cell just like the foregoing Graetzel type cellfor which a light absorption layer with low absoptance per one layer,the roughness factor is increased by using a fine particle film with ahigh porosity in order to increase the surface area and on the otherhand, even in the case of using an acicular crystal, the roughnessfactor can be increased if its aspect ratio is high and the roughnessfactor can further be increased by sintering a micro crystal in thesurrounding of the acicular crystal.

[0060] The transverse cross-section of the acicular crystal is, thoughdiffering corresponding each crystal, triangular, rectangular,hexagonal, and polygonal other than them and includes almost roundcross-section. The respective sides may not necessarily be equal and aresometimes different. As described before, the acicular crystal includesthose with truncated and flat ends beside those with sharpened tips. Thedesirable aspect ratio of the acicular crystal is not lower than 5,preferably not lower than 10, and further preferably not lower than1000, though it depends on the absorptance. Additionally, the diameterof the acicular crystal is preferably 1μm or less and more preferably0.1 μm or less.

[0061] The aspect ratio in this case means the ratio of the length ofthe acicular crystal to the diameter in the case where the acicularcrystal has a round or an approximately round transverse cross-sectionand the ratio of the length to the shortest length of a line passing thegravity center of the cross-section in the case where the acicularcrystal has a polygonal, e.g. hexagonal, cross-section.

[0062] As a material for the acicular crystal and the mixed crystal,those having wide energy gaps are preferable and practically, thosehaving 3 eV or wider energy gaps are preferable. Metal oxides arepreferable to be used as materials for the acicular crystal. As amaterial for the electron acceptive (n-type) crystal, for example, TiO₂,ZnO, SnO₂, or the likes are preferable and as a material for theelectron donative (p-type) crystal, for example, NiO, CuI, or the likesare preferable.

[0063] As a method of acicular crystal formation, a method involvingapplying an acicular crystal powder and firing the powder just like inthe case of production of the foregoing Graetzel cell is applicable. Inthis case, it is preferable that the acicular crystals are approximatelyvertical to a substrate 14 while one ends of the acicular crystals beingjoined to the transparent electrode 15 as shown in FIG. 3B and FIG. 1Brather to that the acicular crystals are parallel to the substrate 14 asshown in the outline cross-section illustrated in FIG. 3A. In additionto that, in the case where no transparent electrode 15 exists and thesubstrate works also as an electrode, one ends of the acicular crystalsare preferably joined to the principal plane of the substrate. The angleformed between the axial direction of the acicular crystals and theprincipal plane of the substrate is preferably 60° or wider and morepreferably 80° or wider.

[0064] As a method of mixed crystal formation, the foregoing methodinvolving applying a mixed crystal powder and firing the powder isapplicable. In this case, it is preferable that the acicular crystalsare approximately vertical to a substrate 14 while one ends of theacicular crystals being joined to the transparent electrode 15 as shownin FIG. 3D and FIG. 1D rather to that the acicular crystals are parallelto the substrate 14 as shown in the outline cross-section illustrated inFIG. 3C. In addition to that, the angle formed between the axialdirection of the acicular crystals and the principal plane of thesubstrate is preferably 60° or wider and more preferably 80° or wider.Also, there are available the method of applying a semiconductor crystal18 after being previously mixed or the method of applying one or moretypes of semiconductor crystals prior and then applying others thereon.The semiconductor crystals 18 are preferably fine particles with 100 nmor smaller, preferably 20 nm or smaller, diameter.

[0065] Other methods for growing an acicular crystal on an electrodesuch as the transparent electrode 15 is further available. Mainly twoways are applicable to carry out the acicular crystal growth: one is bysupplying the crystal components from the outside, including CVD method,PVD method, and electrodeposition method and the other is by causingreaction of the components of electrode to grow the acicular crystal.

[0066] The following are practical ways for the former: a way involvingsteps of forming the undercoating electrode layer (a metal layer) 42 onthe substrate 41 as illustrated in the cross-sectional views of FIGS. 5Aand 5C and then growing an acicular crystal of TiO₂, ZnO, or the like onthe under electrode layer 42 by open-to-atmosphere type CVD method and,if in the case of forming a mixed crystal, further depositing asemiconductor crystal of such as TiO₂, ZnO, or the like thereon andanother way involving steps of growing an acicular crystal of TiO₂, ZnO,or the like directly on the metal substrate 44, which works also as anunder electrode, by open-to-atmosphere type CVD method as illustrated inthe cross-sectional views of FIGS. 5B and 5D and, if in the case offorming a mixed crystal, further applying the semiconductor crystal 18thereto.

[0067] The following are practical ways for the latter: a way involvingsteps of forming the undercoating electrode layer (a metal layer) 42 ofsuch as Ti, Zn or the like on the substrate 41 as illustrated in thecross-sectional views of FIGS. 5A and 5C and then growing an acicularcrystal by oxidizing the surface of the undercoating electrode layer 42or by CVD method and another way involving steps of growing an acicularcrystal by directly oxidizing the metal substrate 44, which works alsoas an under electrode as illustrated in the cross-sectional views ofFIGS. 5B and 5D. A method of growing the acicular crystal from nanoholes is available for the method of controlling the diameter and thegrowth direction of the acicular crystal. For example, as illustrated inthe cross-sectional views of FIGS. 4A to 4D, an aluminium layer with 0.1to 10 μm thickness is formed on the undercoating electrode layer 42 orthe metal substrate 44 and a nano hole layer (a finely porous layer) 43of alumina is formed by anodizing the resultant aluminium layer. Theanodization is carried out using, for example, oxalic acid, phosphoricacid, sulfuric acid, or the like. The gaps between the neighboring nanoholes can be controlled by controlling the voltage for anodization. Thediameter of the nano holes can also be controlled by carrying outetching with a phosphoric acid solution after the anodization. Thesemiconductor acicular crystal is grown through the nano holes bygradually oxidizing the resultant substrate 44 in oxygen atmosphere orsteam-containing atmosphere to oxidize the undercoating electrode layer42 or the naked part of the metal substrate 44 after the nano hole layer43 is formed.

[0068] In the case where the acicular crystal is grown by oxidation, thelength and the diameter can be controlled by the oxidation conditions.

[0069] A structure where the semiconductor crystal 18 exists in thesurface of the semiconductor acicular crystal 17 as illustrated in FIGS.5C and 5D can be formed by forming the acicular crystal with controlleddiameter and growth direction and after that immersing the resultantelectrode in a gel solution containing different types of semiconductorcrystals. Consequently, even in the case where the diameter or thelength of the acicular crystal is insufficient, a semiconductor crystalwith a high roughness factor can be produced and as a result, asemiconductor mixed crystal with scarce effects of grain boundaries onthe movement of electrons or holes can be produced.

[0070] <Regarding Light Absorption Layer>

[0071] Various kinds of semiconductors and coloring agents are usablefor the light absorption layer of the photoelectric conversion devicesof the present invention. An amorphous semiconductor and a directtransition type semiconductor with i-type and a high light absorptioncoefficient are preferable for the semiconductors. A metal complexcoloring agent and/or organic and natural coloring agents such as apolymethine coloring agent, a perylene coloring agent, rose Bengal,Santaline coloring agent, Cyanin coloring agent, or the likes arepreferable for the coloring agents. The coloring agents are preferableto have proper bonding groups for forming bonds to the surface of thesemiconductor fine particle. The preferable bonding groups are COOHgroup, cyano group, PO₃H₂ group, and chelating groups havingπ-conduction such as oxime, dioxime, hydroxyquinoline, salicylate, andα-keto-enolate. Among them, COOH group and P0 ₃H₂ group are especiallypreferable. In the case where the coloring agent to be used for theprevent invention is a metal complex coloring agent, a ruthenium complexcoloring agent {Ru(dcbpy)₂(SCN)₂;(dcbpy=2,2-bipyridine-4,4′-dicarboxylic acid) or the likes) can beusable and it is important for the coloring agent to have stableoxidized and reduced state.

[0072] Further, it is necessary for the electric potential of electronsexcited in the light absorption layer, that is the electric potential(LUMO potential of dye) of dye excited by photoexcitation, and for theelectric potential of the conduction band of the semiconductor to behigher than the electron acceptive potential (the conduction bandpotential of the n-type semiconductor) of the electron acceptive chargetransfer layer and for the electric potential of holes generated in thelight absorption layer by photoexcitation to be lower than the electrondonative potential (the valence band of the p-type semiconductor,potential voltage of the redox pair, or the like) of the electrondonative charge transfer layer. To lower the probability ofrecombination of excited electrons and holes in the periphery of thelight absorption layer is also important to increase the photoelectricconversion efficiency.

[0073] <Regarding Acicular Crystal and Opposite Charge Transfer Layer>

[0074] In the case where an n-type acicular crystal or a mixed crystalis employed, a hole transfer layer is required to be formed on theopposite to the other charge transfer layer while sandwiching a lightabsorption layer 12. On the contrary, in the case where a p-typeacicular crystal or a mixed crystal is employed, an electron transferlayer is required to be formed as a charge transfer layer whilesandwiching a light absorption layer 12. As the charge transfer layer, aredox type transfer layer similar to that of the Graetzel type cell canbe employed. As the redox type charge transfer layer, not only a simplesolution but also a carrier produced from a carbon powder, a materialproduced by gelling an electrolytic substance, or the likes can be used.Also, a molten salt, an ion conductive polymer, an electrochemicallypolymerized organic polymer, etc. may be usable. As the hole transferlayer, a p-type semiconductor such as CuI, CuSCN, NiO, etc. may be used.As the electron transfer layer, an n-type semiconductor such as ZnO,TiO₂, SnO₂, etc. may be used.

[0075] Since the charge transfer layer is required to enter among theacicular crystals or the mixed crystals, a method to be employed is themethod applicable for forming a transfer layer of a liquid or a polymerand the plating method and CVD method applicable for forming a solidtransfer layer.

[0076] <Regarding Electrode>

[0077] An electrode is so formed as to be adjacent to a charge transferlayer and a semiconductor acicular crystal layer. The electrode may beformed in the whole surface of a part of the surface in the outsides ofthose layers. In the case where the charge transfer layer is not of asolid, the electrode is preferably formed in the whole surface from aviewpoint of holding the charge transfer layer. It is also preferable toform a catalyst of Pt, C, or the like on the surface of the electrodeneighboring the charge transfer layer in order to efficiently carry outreduction of, for example, a redox pair.

[0078] A transparent electrode made of ITO (indium tin oxide) and a tinoxide doped with F and Sb are suitable to be used as the electrode inthe light incident side. In the case where the resistance of the layer(a charge transfer layer or a semiconductor acicular crystal layer or asemiconductor mixed crystal layer) adjacent to the electrode in thelight incident side is sufficiently low, a partial electrode, forexample, a finger electrode or the like can be formed as the electrodein the light incident side.

[0079] As the electrode which is not employed in the light incidentside, a metal electrode comprising of Cu, Ag, Al or the like ispreferably used.

[0080] <Regarding Substrate>

[0081] The material and the thickness of a substrate are properlyselected corresponding to the durability required to a photovoltaicforce generating device. The substrate in the light incident side isnecessary to be transparent and a glass substrate, a plastic substrate,or the like is suitable to be used. As the substrate which is notemployed for that in the light incident side, a metal substrate, aceramic substrate, or the like is suitable to be used. It is preferableto form a reflection preventing film of SiO₂ or the like on the surfaceof the substrate in the light incident side.

[0082] It may be possible to make a substrate of a different materialfrom the foregoing electrode no need by using the electrode also as thesubstrate.

[0083] <Regarding Sealing>

[0084] Though it is not illustrated in FIGS., a photoelectric conversiondevice of the present invention is preferably sealed in at least partsbesides the substrates from a viewpoint of improvement of the weatheringresistance. An adhesive and resin may be used as the sealing material.In the case where the light incident side is sealed, the sealingmaterial to be used has to be transparent.

[0085] No need to say, the present invention is not limited to coloringagent sensitizing type photoelectric conversion devices but applicablewidely to photoelectric conversion devices constituted as to have alarge surface area to increase the light absorptance.

EXAMPLES

[0086] Present invention will be further described with followingexamples.

Example 1

[0087] A production example of a photoelectric conversion devicecomprising a semiconductor acicular crystal layer formed using a rutiletype acicular crystal powder as an electron acceptive charge transferlayer will be described in the present example.

[0088] A slurry was produced by mixing 6 g of rutile type TiO₂ crystalhaving 100 to 200 nm diameter and the length about 10 times as long asthe diameter (aspect ratio about 10) with 10 g of water, 0.2 g ofacetylacetone, and 0.2 g of Triton X. The slurry was applied to aconductive glass (a glass plate on which a F-doped SnO₂ (sheetresistance 100Ω/□) film was formed) in about 50 μm thickness and 1 cm²square using a spacer and then the resultant glass was fired at 450° C.for 1 hour in oxygen gas flow at 10 sccm to obtain a conductive glassbearing a TiO₂ acicular crystal layer. The thickness of the TiO₂semiconductor acicular crystal layer (an electron acceptive chargetransfer layer) after firing was about 10 μm.

[0089] As dye, Ru(dcbpy)₂(SCN)₂ was dissolved in distilled ethanol andthe above described conductive glass bearing the TiO₂ acicular crystallayer was immersed in the solution for 30 minutes to adsorb the coloringagent to the acicular crystal layer and then the conductive glass wastaken out of the solution and dried at 80° C.

[0090] A mixed solution (a redox pair: I⁻/I₃ ⁻) containing 0.46 M oftetrapropylammonium iodide and iodine (0.06 M) as a solute and 80 vol. %of ethylene carbonate as a solvent was produced. The solution wasdropwise applied to the TiO₂ acicular crystal layer of the conductiveglass bearing the TiO₂ acicular crystal layer.

[0091] Another conductive glass (a glass plate on which a F-doped SnO₂(sheet resistance 100 Ω/□) film was formed) bearing a platinum layer of1 nm thickness formed by sputtering was produced and this conductiveglass and the conductive glass bearing the TiO₂ acicular crystal layerwere set on the opposite to each other as to set the platinum layer andthe TiO₂ acicular crystal layer in the inner side and the foregoingmixed solution was held between both glass plates to obtain aphotoelectric conversion device.

[0092] As a comparison, a photoelectric conversion device was fabricatedin the same manner except that a TiO₂ powder containing anatase typefine particle with about 20 nm particle diameter as a main component wasused.

[0093] Light was radiated from a 500 W xenon lamp equipped with aultraviolet-cutting filter to the side of the TiO₂ acicular crystallayer-bearing conductive glass of the respective devices and the valuesof the photoelectric current were measured. In the same manner, lightwas radiated to the side of the platinum layer-bearing conductive glassof the devices and the values of photoelectric current by photoelectricconversion reaction. As a result, the open-circuit voltage and the fillfactor of the device of the present invention were both higher by about5% than those of the device of the comparison in the case of radiatinglight to the devices from the side of the conductive glass bearing theTiO₂ acicular crystal layer and both by about 7% in the case ofradiating light to the devices from the side of the conductive layerbearing the platinum layer. The difference is supposedly attributed tothe decrease of the internal resistance of the electron acceptor-typecharge transfer layer owing to use of the acicular crystals.

Example 2

[0094] A device using a ZnO acicular crystal and a device using a SnO₂acicular crystal instead of the TiO₂ acicular crystal were fabricated.The diameter of the ZnO acicular crystal used for the present inventionwas about 50 nm and the length was about 5 times as long as the diameterand the diameter of the SnO₂ acicular crystal used was about 300 nm andthe length was about 10 times as long as the diameter. The same methodof producing the device of the Example 1 was applied for the respectiveproduction methods and the same evaluation method of the Example 1 wascarried out. As a result, the open-circuit voltage values and the fillfactors of both devices at were both higher by about 3% than those ofthe devices of comparison (a device using a ZnO powder and a deviceusing a SnO₂ powder) in the case of radiating the light from the side ofthe conductive glass bearing the acicular crystal layer and both of theopen-circuit voltage values and the fill factors were higher by about 5%in the case of radiating the light from the side of the conductive glassbearing the platinum layer.

Example 3

[0095] A production example of a photoelectric conversion devicecomprising a semiconductor acicular crystal layer formed by oxidizing ametal material will be described with reference of FIGS. 5A to 5D in thepresent example.

[0096] A substrate was produced by forming a Ti undercoating electrodelayer 42 of 3 μm thickness on a quartz substrate 41 and a Ti substrate(a metal substrate) 44 was produced and the respective substrates wereimmersed in a 0.3 M oxalic acid and 40 V voltage was applied to slightlyanodize the Ti surface. The resultant substrates were fired at 700° C.for 10 hours in He gas current containing 10 ppm of oxygen at 100 sccmflow speed. Rutile type TiO₂ acicular crystals were grown from theundercoating metal layer and the substrate on the Ti undercoating metallayer 42 and the Ti substrate 44 after firing as illustrated in FIGS. 5Aand 5B. The diameter of the TiO₂ acicular crystals was 0.1 to 1 μm andthe length was 10 to 100 times as long as the diameter.

[0097] The same coloring agent as that used for the Example 1 wasadsorbed in the surface of the acicular crystals in the same manner asthat of the Example 1 and a photoelectric conversion device wasfabricated in the same manner as that of the Example 1, except that aconductive glass (a glass plate on which a F-doped SnO₂ (sheetresistance 100 Ω/□) film was formed) bearing a graphite layer (about 1nm thickness) was used instead of the conductive glass bearing theplatinum layer.

[0098] As a comparison, a photoelectric conversion device was fabricatedin th same manner using a TiO₂ powder containing anatase type fineparticle with about 20 nm particle diameter as a main component.

[0099] The photoelectric current value was measured in the same manneras that for the Example 1. The light incidence was carried out from theside of the conductive glass bearing the graphite layer. As a result,the open-circuit voltage and the fill factor of the device of thepresent example were both higher by about 10% than those of the deviceof the comparison. The difference is supposedly attributed to thedecrease of the internal resistance of the electron acceptor-type chargetransfer layer owing to use of the acicular crystals.

Example 4

[0100] A production example of a photoelectric conversion devicecomprising semiconductor acicular crystals grown from nano holes byoxidizing a metal material will be described with reference of FIGS. 4Ato 4D in the present example.

[0101] A substrate was produced by forming a Ti undercoating electrodelayer 42 of 3 μm thickness on a quartz substrate 41 and a Ti substrate(a metal substrate) 44 was produced and the Ti surfaces of therespective substrates were coated with Al layers with 0.5 μm thickness.Then, the respective substrates were immersed in a 0.3 M oxalic acid and40 V voltage was applied to slightly anodize the Ti surfaces. Afterthat, the respective substrates were immersed in 5 wt. % phosphoric acidfor 40 minutes. By that treatment, nano hole layers 43 having a largenumber of nano holes with about 50 nm diameter at about 100 nm gaps wereformed on the alumina layers formed by anodization. The resultantsubstrates were then fired at 700° C. for 10 hours in He gas currentcontaining 10 ppm of oxygen at 100 sccm flow speed. Rutile type TiO₂acicular crystals were grown in the Ti undercoating metal layer 42 andthe Ti substrate 44 after firing as illustrated in FIGS. 5A and 5B. Thediameter of the TiO₂ acicular crystals was 0.02 to 0.05 μm and thelength was 20 to 500 times as long as the diameter.

[0102] The same coloring agent as that used for the Example 3 wasadsorbed in the surface of the acicular crystals in the same manner asthat of the Example 3 and a photoelectric conversion device wasfabricated in the same manner as that of the Example 3.

[0103] As a comparison, a photoelectric conversion device was fabricatedin the same manner using a TiO₂ powder containing anatase type fineparticle with about 20 nm particle diameter as a main component.

[0104] The photoelectric current value was measured in the same manneras that for the Example 1. The light incidence was carried out from theside of the conductive glass bearing the graphite layer. As a result,the open-circuit voltage and the fill factor of the device of thepresent example were both higher by about 15% than those of the deviceof the comparison. The difference is supposedly attributed to thedecrease of the internal resistance of the electron acceptor-type chargetransfer layer owing to use of the acicular crystals. Moreover, it issupposedly attributed to the high aspect ratio and the roughness factorimprovement of the acicular crystals.

Example 5

[0105] A production example of a photoelectric conversion devicecomprising semiconductor acicular crystal layers grown using anopen-to-atmosphere type CVD will be described with reference of FIGS. 5Ato 5D and FIG. 7 in the present example.

[0106]FIG. 7 illustrates a simplified figure of an open-to-atmospheretype CD apparatus employed for the present example and in the figure, 71denotes a nitrogen bomb, 72 a flow meter, 73 a raw material evaporator,74 a nozzle, 75 an object substrate to be treated, and 76 a substrateheating stand.

[0107] A substrate was produced by forming an Al undercoating electrodelayer 42 of 3 μm thickness on a quartz substrate 41 and an Al substrate(a metal substrate) 44 was produced and the substrates 75 as objectsubstrates to be treated were respectively set on the substrate heatingstand 76 of the CVD apparatus. Then, bisacetylacetonatozinc (II) insolid phase was put in the raw material evaporator 73 and evaporated byheat at 115° C. While the flow rate being controlled by the flow meter72, nitrogen gas was supplied from the nitrogen bomb 71 to the apparatusand the evaporated bisacetylacetonatozinc (II) was sprayed to thesubstrates 75 from the nozzle 74. By such a treatment, ZnO acicularcrystals were grown from the undercoating electrode layer and thesubstrate on the surface of Al undercoating electrode layer 42 and onthe surface of the Al substrate 44 as illustrated in FIGS. 5A, 5B. Thediameter of the ZnO acicular crystals was about 1 μm and the length was10 to 100 times as long as the diameter.

[0108] The same coloring agent as that used for the Example 3 wasadsorbed in the surface of the acicular crystals in the same manner asthat of the Example 3 and a photoelectric conversion device wasfabricated in the same manner as that of the Example 3.

[0109] As a comparison, a photoelectric conversion device was fabricatedin the same manner using a thermally treated ZnO powder with about 1 μmparticle diameter.

[0110] The photoelectric current value was measured in the same manneras that for the Example 1. The light incidence was carried out from theside of the conductive glass bearing the graphite layer. As a result,the open-circuit voltage and the fill factor of the d vice of thepresent example were both higher by about 20% than those of the deviceof the comparison. The difference is supposedly attributed to thedecrease of the internal resistance of the electron acceptor-type chargetransfer layer owing to use of the acicular crystals. Moreover, it issupposedly attributed to the high aspect ratio and the roughness factorimprovement of the acicular crystals.

[0111] Also, in the case where a ZnO layer and an Al layer were formedon Ti substrates to obtain the object substrates 75 to be treated andthen alumina nano holes were formed in the same manner as that of theExample 4, ZnO acicular crystals were found grown through the aluminanano holes from the ZnO layer and a photoelectric conversion devicefabricated using the substrates had open-circuit voltage and fill factorboth higher by about 20% than those of a device of comparison.

Example 6

[0112] A production example of a photoelectric conversion devicecomprising semiconductor acicular crystal layers grown using anopen-to-atmosphere type CVD, as same as the Example 5, will be describedwith reference of FIGS. 5A to 5D and FIG. 7 in the present example.

[0113] As an object substrate 75 to be treated, a glass plate 41 onwhich a F-doped SnO₂ layer 42 (sheet resistance 10 Ω/□) was formed wasemployed and a ZnO acicular crystals were grown on the SnO₂ layer 42 inthe same manner as that of the Example 5. The diameter of the ZnOacicular crystals was about 1 μm and the length was 10 to 100 times aslong as the diameter.

[0114] After that, a photoelectric conversion device was fabricated inthe same manner as that of the Example 5, except that CuI, which is ap-type semiconductor, was employed for the charge transfer layer 12.Practically, CuI was dissolved in anhydrous acetonitrile and depositedon the surface of a mesoscopic ZnO layer (an acicular crystal layer)bearing dye. The substrate 41 bearing the charge transfer layer 12 wasoverlaid on the conductive glass bearing the graphite layer to give asolid chemical solar cell (a photoelectric conversion device).

[0115] A photoelectric conversion device was fabricated using athermally treated ZnO powder with about 1 μm particle diameter in thesame manner for comparison.

[0116] The photoelectric current value was measured in the same manneras that for the Example 1. The light incidence was carried out from theside of the conductive glass bearing the graphite layer. As a result,the open-circuit voltage and the fill factor of the device of thepresent example were both higher by about 20% than those of the deviceof the comparison. The difference is supposedly attributed to thedecrease of the internal resistance of the electron acceptor-type chargetransfer layer owing to use of the acicular crystals. Moreover, it issupposedly attributed to the high aspect ratio and the roughness factorimprovement of the acicular crystals.

Example 7

[0117] A production example of a photoelectric conversion devicecomprising an electron acceptive charge transfer layer formed using arutile type acicular crystal powder will be described in the presentexample.

[0118] A slurry was produced by mixing 3 g of rutile type TiO₂ acicularcrystal having 200 to 300 nm diameter and the length about 10 times aslong as the diameter and 3 g of anatase type TiO₂ micro crystal (P25)having about 20 nm diameter with 10 mL (milliliter) of water, 0.2 mL ofacetylacetone, and 0.2 mL of Triton X (registered trade name: producedby Union Carbide Corp.). The slurry was applied to a conductive glass(F-doped SnO₂, 100 Ω/□) in about 50 μm thickness and 1 cm² square usinga spacer and then the resultant glass was fired at 450° C. for 1 hour inoxygen gas flow at 100 mL/min (sccm).

[0119] The thickness of the obtained TiO₂ acicular crystal layer afterfiring was about 10 μm. Ru((bipy)₂(COOH)₂(SCN)₂), which was a Ru complexsalt reported by Graetzel, was used as dye. The coloring agent wasdissolved in distilled ethanol and the TiO₂ electrode was immersed inthe resultant solution for 120 minutes to adsorb the coloring agent tothe electrode and then the electrode was taken out of the solution anddried at 80° C. On the other hand, another conductive glass (F-dopedSnO₂, 10 Ω/□) bearing a platinum layer of 1 nm thickness formed bysputtering was employed as a counterpart electrode and I⁻/I₃ ⁻was usedas a redox pair. A mixed solution employed for the present examplecontained 0.46 mol/L of tetrapropylammonium iodide and 0.06 mol/L ofiodine as solutes and 80 vol. % of ethylene carbonate and 20 vol. % ofacetonitrile as solvents. The solution was dropwise applied to theTiO₂-bearing conductive glass and the mixed solution was held betweenthe conductive glass bearing the TiO₂ and the counterpart electrode toobtain a cell.

[0120] As a comparison, a cell using only P25 was fabricated in the samemanner.

[0121] Light was radiated from a 500 W xenon lamp equipped with aultraviolet-cutting filter to the side of the conductive glass bearingTiO₂ or to the side of the counterpart electrode. The values of thephotoelectric current generated at that time by the photoelectricconversion reaction were measured. As a result, the open-circuit voltageand the fill factor of the cell of the present invention were bothhigher by about 5% than those of the cell of the comparison and,especially in the case of radiating light to the cells from thecounterpart electrodes, both were higher by about 7%. The difference issupposedly attributed to the decrease of the internal resistance of theelectron acceptor-type charge transfer layer owing to use of the mixedcrystal.

Example 8

[0122] Similar experiments to that of the Example 7 were carried outusing a ZnO acicular crystal and a SnO₂ acicular crystal, respectively,instead of the TiO₂ acicular crystal.

[0123] The ZnO acicular crystal used for the present invention had atetrapod-like shape, the diameter of about 1 μm diameter, and the lengthabout 5 times as long as the diameter and the SnO₂ acicular crystal usedhad the diameter of about 0.5 μm and the length about 10 times as longas the diameter. The same method of producing the device of the Example7 was applied for the respective production methods and the sameevaluation method as that of the Example 1 was carried out. As a result,the open-circuit voltage values and the fill factors of both deviceswere both higher by about 3% than those of the devices of comparison (adevice using a ZnO powder and a device using a SnO₂ powder) in the caseof radiating the light from the side of the conductive glass bearing themixed crystal and both of the open-circuit voltage values and the fillfactors were higher by 5% or more in the case of radiating the lightfrom the side of the counterpart electrodes. That is supposedlyattributed to the decrease of the internal resistance of the electronacceptor-type charge transfer layer owing to use of the mixed crystal.

Example 9

[0124] A production example of semiconductor acicular crystals byoxidizing a metal material will be described with reference of FIGS. 5Ato 5D in the present example.

[0125] A substrate was produced by forming a Ti undercoating electrodelayer 42 of 3 μm thickness on a quartz substrate 41 and a substrate of aTi plate 44 was produced and the respective Ti surfaces were slightlyanodized at 40 V voltage in 0.3 mol/L oxalic acid. The resultantsubstrates were then fired at 700° C. for 10 hours in flow of He gascontaining 10 ppm oxygen at 100 mL/min (sccm) flow rate. Rutile typeTiO₂ acicular crystals were found on the Ti undercoating metal layer andthe Ti substrate surface after firing growing from the substrates asillustrated in FIGS. 5C and 5D. The diameter of the TiO₂ acicularcrystals was 0.1 to 2 μm and the length was 10 to 100 times as long asthe diameter. The resultant substrates were then immersed in a slurryproduced by mixing 3 g of anatase type TiO₂ micro crystal (P25) havingabout 20 nm particle diameter with 40 mL of water, 0.2 mL ofacetylacetone, and 0.2 mL of Triton X and after that the substrates wereagain fired at 450° C. for 1 hour in oxygen gas flow at 100 mL/min(sccm). Dye was adsorbed on the surface of the obtained acicularcrystals in the same manner as that of the Example 1. On the other hand,another conductive glass (F-doped SnO₂, 10 Ω/□) bearing graphite ofabout 1 nm thickness was employed as a counterpart electrode and I⁻/I₃⁻was used as a redox pair. As same as the solution employed for theExample 7, a mixed solution employed for the present example containedtetrapropylammonium iodide (0.46 mol/L) and iodine (0.06 mol/L) assolutes and ethylene carbonate (80 vol. %) and acetonitrile (20 vol. %)as solvents. The solution was dropwise applied to the TiO₂-bearingconductive glass and the mixed solution was held between the conductiveglass bearing the TiO₂ and the counterpart electrode to obtain a cell.

[0126] As a comparison, a cell using only P25 was fabricated in the samemanner.

[0127] In the same manner as that of the Example 7, light was radiatedfrom a 500 W xenon lamp equipped with a ultraviolet-cutting filter fromthe side of the counterpart electrode. The values of the photoelectriccurrent generated at that time by the photoelectric conversion reactionwere measured. As a result, the open-circuit voltage and the fill factorof the cell of the present invention were both higher by about 10%. Thatis supposedly attributed to the decrease of the internal resistance ofthe electron acceptor-type charge transfer layer owing to use of theacicular crystal.

Example 10

[0128] A production example of semiconductor acicular crystals from nanoholes by oxidizing a metal material will be described with reference ofFIGS. 4A to 4D in the present example.

[0129] A substrate was produced by forming a Ti undercoating electrodelayer 42 of 3 μm thickness on a quartz substrate 41 and a substrate of aTi plate 44 was produced and the respective Ti surfaces were coated with0.5 μm thick Al films. The Al films were anodized at 40 V voltage in 0.3mol/L oxalic acid and then immersed in 5 wt.% phosphoric acid for 40minutes. By the treatment, a large number of nano holes with about 50 nmdiameter at about 100 nm gaps were formed in the alumina layers 43formed by anodization. The resultant substrates were then fired at 700°C. for 10 hours in He gas current containing 10 ppm of oxygen at 100mL/min (sccm) flow speed. Rutile type TiO₂ acicular crystals 17 werefound in the Ti undercoating metal layer and the Ti substrate surfaceafter firing as illustrated in FIGS. 4C and 4D, growing from the nanoholes of the electrodes. The diameter of the TiO₂ acicular crystals was0.02 to 0.05 μm and the length was 20 to 500 times as long as thediameter. The resultant substrates were then immersed in a slurryproduced by mixing 3 g of anatase type TiO₂ micro crystal (P25) havingabout 20 nm particle diameter with 40 mL of water, 0.2 mL ofacetylacetone, and 0.2 mL of Triton X and after that the substrates wereagain fired at 450° C. for 1 hour in oxygen gas flow at 100 mL/min(sccm).

[0130] Further, dye was adsorbed on the surface of the obtained acicularcrystals in the same manner as that of the Example 7. On the other hand,conductive glass (F-doped SnO₂, 10 Ω/□) bearing graphite of about 1 nmthickness was employed as a counterpart electrode and I⁻/I₃ ⁻was used asa redox pair. As same as the Example 1, a mixed solution containingtetrapropylammonium iodide (0.46 mol/L) and iodine (0.06 mol/L) assolutes and ethylene carbonate (80 vol.%) and acetonitrile (20 vol.%) assolvents was employed. The solution was dropwise applied to theTiO₂-bearing conductive glass and the mixed solution was held betweenthe conductive glass bearing the TiO₂ and the counterpart electrode toobtain a cell.

[0131] As a comparison, a cell using only P25 was fabricated in the samemanner.

[0132] In the same manner as that of the Example 7, light was radiatedfrom a 500 W xenon lamp equipped with a ultraviolet-cutting filter fromthe side of the counterpart electrode. The values of the photoelectriccurrent generated at that time by the photoelectric conversion reactionwere measured. As a result, the open-circuit voltage and the fill factorof the cell of the present invention were both higher by about 5%. Thatis supposedly attributed to the decrease of the internal resistance ofthe electron acceptor-type charge transfer layer owing to use of theacicular crystals.

Example 11

[0133] A production example of semiconductor acicular crystals using anopen-to-atmosphere type CVD method will be described with reference ofFIGS. 5A to 5D and FIG. 7 in the present example.

[0134] A substrate was produced by forming an Al undercoating electrodelayer 42 of 3 μm thickness on a quartz substrate 41 and an Al substrate44 was produced and these substrates were respectively set on thesubstrate heating stand 76 of the CVD apparatus. Then,bisacetylacetonatozinc (II) in solid phase was put in a raw materialevaporator 73 and evaporated by heat at 115° C. While being carried withnitrogen, the evaporated bisacetylacetonatozinc (II) was sprayed to theAl substrates 75 from a nozzle 74 After the treatment, ZnO acicularcrystals were found grown on the Al undercoating electrode layer and theAl substrate surface as illustrated in FIGS. 5A, 5B. The diameter of theZnO acicular crystals was about 1 μm and the length was 10 to 100 timesas long as the diameter. The resultant substrates were then immersed ina slurry-like solution produced by mixing 3 g of rutile type TiO₂acicular crystal and 3 g of anatase type TiO₂ micro crystal (P25) havingabout 20 nm diameter with 40 mL of water, 0.2 mL of acetylacetone, and0.2 mL of Triton X and after that the substrates were fired at 450° C.for 1 hour in oxygen gas flow at 100 mL/min (sccm). Then, dye wasadsorbed on the surface of the acicular crystals in the same manner asthat of the Example 1. On the other hand, conductive glass (F-dopedSnO₂, 10 Ω/□) bearing graphite of 1 nm thickness was employed as acounterpart electrode and I⁻/I₃ ⁻was used as a redox pair. As same asthe Example 7, a mixed solution containing tetrapropylammonium iodide(0.46 mol/L) and iodine (0.06 mol/L) as solutes and ethylene carbonate(80 vol.%) and acetonitrile (20 vol.%) as solvents was employed. Thesolution was dropwise applied to the ZnO-bearing conductive substrateand the mixed solution was held between the conductive substrate bearingthe ZnO and the counterpart electrode to obtain a cell.

[0135] As a comparison, a cell using a thermally treated ZnO powdermainly containing particles of about 1 μm particle diameter wasfabricated in the same manner.

[0136] In the same manner as that of the Example 7, light was radiatedfrom a 500 W xenon lamp equipped with a ultraviolet-cutting filter fromthe counterpart electrode side. The values of the photoelectric currentgenerated at that time by the photoelectric conversion reaction weremeasured. As a result, the open-circuit voltage and the fill factor ofthe cell of the present invention were both higher by about 7%. That issupposedly attributed to the decrease of the internal resistance of theelectron acceptor-type charge transfer layer owing to use of theacicular crystals.

Example 12

[0137] A production example of semiconductor acicular crystals using anopen-to-atmosphere type CVD method will be described with reference ofFIGS. 5A to 5D and FIG. 7 in the present example.

[0138] Conductive glass (F-doped SnO₂, 10 Ω/□)was produced by forming aF-doped SnO₂ 42 film on a substrate glass 44 and the substrate was seton a substrate heating stand 76 of the CVD apparatus. Then,bisacetylacetonatozinc (II) in solid phase was put in a raw materialevaporator 73 and evaporated by heat at 115° C. While being carried withnitrogen, the evaporated bisacetylacetonatozinc (II) was sprayed to theconductive glass substrate 75 from a nozzle 74. After the treatment, ZnOacicular crystals were found grown on the conductive glass surface asillustrated in FIG. 5C. The diameter of the ZnO acicular crystals wasabout 1 μm and the length was 10 to 100 times as long as the diameter.The resultant substrate was then immersed in a slurry-like solutionproduced by mixing 3 g of rutile type TiO₂ acicular crystal and 3 g ofanatase type TiO₂ micro crystal (P25) having about 20 nm diameter with40 mL of water, 0.2 mL of acetylacetone, and 0.2 mL of Triton X andafter that the substrate was fired at 450° C. for 1 hour in oxygen gasflow at 100 mL/min (sccm). Then, dye was adsorbed on the surface of theacicular crystals in the same manner as that of the Example 1. On theother hand, conductive glass (F-doped SnO₂, 10 Ω/□) bearing graphite ofabout 1 nm thickness was employed as a counterpart electrode and CuI wasused as a p-type semiconductor. CuI was at first dissolved in anhydrousacetonitrile and then deposited on the interfaces of the mesoscopic ZnOfilm bearing the coloring agent. The solid electrode produced in such amanner and the counterpart electrode were overlaid to each other toobtain a solid chemical solar cell.

[0139] As a comparison, a cell using a thermally treated ZnO powdermainly containing particles of about 1 μm particle diameter wasfabricated in the same manner.

[0140] In the same manner as that of the Example 7, light was radiatedfrom a 500 W xenon lamp equipped with a ultraviolet-cutting filter fromthe counterpart electrode side. The values of the photoelectric currentgenerated at that time by the photoelectric conversion reaction weremeasured. As a result, the open-circuit voltage and the fill factor ofthe cell of the present invention were both higher by about 7%. That issupposedly attributed to the decrease of the internal resistance of theelectron acceptor-type charge transfer layer owing to use of theacicular crystals.

Example 13

[0141] A production example of a photoelectric conversion device using arutile type acicular crystal powder for an electron acceptive chargetransfer layer will be described in the present example.

[0142] A slurry was produced by mixing 6 g of rutile type TiO₂ acicularcrystal having 200 to 300 nm diameter and the length about 10 times aslong as the diameter with 10 mL (milliliter) of water, 0.2 mL ofacetylacetone, and 0.2 mL of Triton X. The slurry was applied to aconductive glass (F-doped SnO₂, 100 Ω/□) in about 50 μm thickness and 1cm² square using a spacer and then the resultant glass was fired at 450°C. for 1 hour in oxygen gas flow at 100 mL/min (sccm). The resultantsubstrate was then immersed in a slurry-like solution produced by mixing3 g of anatase type TiO₂ micro crystal (P25) having about 20 nm diameterwith 40 mL of water, 0.2 mL of acetylacetone, and 0.2 mL of Triton X andafter that, the substrate was fired at 450° C. for 1 hour in oxygen gasflow at 100 mL/min (sccm). Then, dye was adsorbed on the surface of theacicular crystals in the same manner as that of the Example 7. Then,conductive glass (F-doped SnO₂, 10 Ω/□)bearing graphite of about 1 nmthickness was employed as a counterpart electrode and I⁻/I₃ ⁻was used asa redox pair. As same as the Example 7, a mixed solution containingtetrapropylammonium iodide (0.46 mol/L) and iodine (0.06 mol/L) assolutes and ethylene carbonate (80 vol. %) and acetonitrile (20 vol. %)as solvents was employed. The solution was dropwise applied to theTiO₂-bearing conductive substrate and the mixed solution was heldbetween the conductive substrate bearing the TiO₂ and the counterpartelectrode to obtain a cell.

[0143] As a comparison, a cell using only P25 was fabricated in the samemanner.

[0144] Light was radiated from a 500 W xenon lamp equipped with aultraviolet-cutting filter from the side of the conductive substratebearing the TiO₂ and to the side of the counterpart electrode. Thevalues of the photoelectric current generated at that time by thephotoelectric conversion reaction were measured. As a result, theopen-circuit voltage and the fill factor of the cell of the presentinvention were both higher by about 3% and especially, higher by about5% in the case where light was radiated to the counterpart electrodeside. That is supposedly attributed to the decrease of the internalresistance of the electron acceptor-type charge transfer layer owing touse of the acicular crystals.

[0145] As described above, the present invention can provide aphotoelectric conversion device in which the transfer and the movementof electrons and holes are smoothly carried out, whose internalresistance and recombination probability is low, and which has a highconversion efficiency.

[0146] Also, the present invention can provide a photoelectricconversion device comprising a semiconductor electrode provided with alight absorption layer of dye and a charge transfer layer of anelectrolytic solution with high impregnation and movement speed.

[0147] Further, the present invention can provide a photoelectricconversion device with high open-circuit voltage.

[0148] Moreover, the present invention can provide a method of producingphotoelectric conversion devices provided with the foregoingcharacteristics.

What is claimed is:
 1. A photoelectric conversion device comprising at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, wherein either one of the charge transfer layers is a semiconductor acicular crystal layer comprising aggregate of acicular crystals.
 2. The photoelectric conversion device according to claim 1, wherein the diameters of the acicular crystals are 1 μm or less.
 3. The photoelectric conversion device according to claim 1, wherein an aspect ratio of the acicular crystal is 5 or more when the aspect ratio is defined as the ratio of the length to the diameter of the acicular crystal or as the ratio of the length of the acicular crystal to the length of a shortest line in a transverse cross-section passing the gravity center of the acicular crystal.
 4. The photoelectric conversion device according to claim 1, wherein an aspect ratio of the acicular crystal is 10 or more when the aspect ratio is defined as the ratio of the length to the diameter of the acicular crystal or as the ratio of the length of the acicular crystal to the length of a shortest line in a transverse cross-section passing the gravity center of the acicular crystal.
 5. The photoelectric conversion device according to claim 1, wherein the semiconductor acicular crystal layer is provided on a substrate, one end of the acicular crystal forming the semiconductor acicular crystal layer is bonded to a principal plane of the substrate, and the angle formed between the axial direction of the acicular crystal and the principal plane of the substrate is 60° or more.
 6. The photoelectric conversion device according to claim 1, wherein the semiconductor acicular crystal layer is provided on a substrate with an electrode, one end of the acicular crystal forming the semiconductor acicular crystal layer is bonded to the electrode, and the angle formed between the axial direction of the acicular crystal and the principal plane of the substrate is 60° or more.
 7. The photoelectric conversion device according to claim 1, wherein the light absorption layer comprises dye.
 8. The photoelectric conversion device according to claim 1, wherein the acicular crystals comprise a metal oxide.
 9. The photoelectric conversion device according to claim 8, wherein the acicular crystals comprise titanium oxide.
 10. The photoelectric conversion device according to claim 8, wherein the acicular crystals comprise zinc oxide.
 11. The photoelectric conversion device according to claim 8, wherein the acicular crystals comprise tin oxide.
 12. The photoelectric conversion device according to claim 1, wherein a part of the acicular crystals exists in fine pores of a finely porous layer having a number of fine pores.
 13. A method of producing a photoelectric conversion device which comprises at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, the method comprising applying a solution containing acicular crystals on a substrate and firing the substrate to form a semiconductor acicular crystal layer comprising aggregate of acicular crystal on the substrate and utilizing the semiconductor acicular crystal layer as either one of the charge transfer layers.
 14. A method of producing a photoelectric conversion device which comprises at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, the method comprising forming a semiconductor acicular crystal layer comprising aggregate of acicular crystals on a substrate by a CVD process and utilizing the semiconductor acicular crystal layer as either one of the charge transfer layers.
 15. The method of producing a photoelectric conversion device according to claim 14, comprising the steps of providing an aluminium layer on a surface of the substrate, anodizing the aluminium layer to form a finely porous alumina layer, and growing the semiconductor acicular crystals through the alumina fine pores by a CVD process
 16. A method of producing a photoelectric conversion device which comprises at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, the method comprising oxidizing a surface of a substrate to form a semiconductor acicular crystal layer comprising aggregate of acicular crystals on the substrate and utilizing the semiconductor acicular crystal layer as either one of the charge transfer layers.
 17. The method of producing a photoelectric conversion device according to claim 16, comprising the steps of providing an aluminium layer on a surface of the substrate, anodizing the aluminium layer to form a finely porous alumina layer, and oxidizing at least a part of the substrate to grow the semiconductor acicular crystals through the alumina fine pores.
 18. The method of producing a photoelectric conversion device according to claim 16, wherein a substrate comprising any one of titanium, zinc, and tin at least in the surface is used as the substrate.
 19. The method of producing a photoelectric conversion device according to claim 13 or 16, wherein a substrate having an electrode on the surface thereof is used as the substrate.
 20. A photoelectric conversion device comprising at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, wherein either one of the charge transfer layers is a semiconductor layer comprising a mixture with two or more kinds of different morphologies or compositions and at least one of the kinds of the semiconductor layer is an acicular crystal.
 21. The photoelectric conversion device according to claim 20, wherein the diameter of the acicular crystal is 1 μm or less.
 22. The photoelectric conversion device according to claim 20, wherein the aspect ratio is 5 or more when the aspect ratio is defined as the ratio of the length to the diameter of the acicular crystal or as the ratio of the length of the acicular crystal to the length of a shortest line in a transverse cross-section passing the gravity center of the acicular crystal.
 23. The photoelectric conversion device according to claim 20, wherein an aspect ratio is 10 or more when the aspect ratio is defined as the ratio of the length to the diameter of the acicular crystal or as the ratio of the length of the acicular crystal to the length of a shortest line in a transverse cross-section passing the gravity center of the acicular crystal.
 24. The photoelectric conversion device according to claim 20, wherein one end of the acicular crystal is bonded to an electrode provided on a substrate and the angle formed between the axial direction of the acicular crystal and the principal plane of the substrate is 60° or more.
 25. The photoelectric conversion device according to claim 20, wherein the semiconductor other than the acicular crystal in the mixture is a fine particle with a diameter of 100 nm diameter or less.
 26. The photoelectric conversion device according to claim 25, wherein the fine particle exists on a surface of the acicular crystal.
 27. The photoelectric conversion device according to claim 20, wherein the material of the light absorption layer is dye.
 28. The photoelectric conversion device according to claim 20, wherein the mixture comprises a metal oxide.
 29. The photoelectric conversion device according to claim 28, wherein at least one kind of the mixture is titanium oxide.
 30. The photoelectric conversion device according to claim 28, wherein at least one kind of the mixture is zinc oxide.
 31. The photoelectric conversion device according to claim 28, wherein at least one material of the mixture is tin oxide.
 32. The photoelectric conversion device according to claim 20, wherein a part of the acicular crystal exists in a fine pore of a finely porous layer having a number of fine pores.
 33. A method of producing a photoelectric conversion device which comprises at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, the method comprising applying a semiconductor mixture solution comprising a semiconductor mixture with two or more kinds of different morphologies or compositions on a substrate and firing the substrate to form a semiconductor mixed crystal layer on the substrate, and utilizing the semiconductor mixed crystal layer as either one of the charge transfer layers.
 34. A method of producing a photoelectric conversion device which comprises at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, the method comprising the steps of applying a solution containing a semiconductor acicular crystal on a substrate and firing the substrate to form an acicular semiconductor crystal layer, further depositing a single substance or a mixture with a different morphology or composition from that of the acicular crystal to the semiconductor layer to form a semiconductor mixed crystal layer on the substrate, and utilizing the semiconductor mixed crystal layer as either one of the charge transfer layers.
 35. A method of producing a photoelectric conversion device which comprises at least an electron acceptive charge transfer layer, an electron donative charge transfer layer, and a light absorption layer existing between the charge transfer layers, the method comprising the steps of growing an acicular crystal on a substrate, depositing to the acicular crystal a single substance or a mixture with a different morphology or composition from that of the acicular crystal to form a semiconductor mixed crystal layer on the substrate, and utilizing the semiconductor mixed crystal layer as either one of the charge transfer layers.
 36. The method of producing a photoelectric conversion device according to claim 35, comprising the step of growing the acicular crystal on the substrate by a CVD process.
 37. The method of producing a photoelectric conversion device according to claim 36, comprising the steps of forming an aluminium layer on a surface of the substrate, anodizing the aluminium layer to form a finely porous alumina layer, and growing a semiconductor acicular crystal through the fine pores of the finely porous alumina layer by a CVD process.
 38. The method of producing a photoelectric conversion device according to claim 35, comprising the step of oxidizing a surface of the substrate to grow the acicular crystal on the substrate.
 39. The method of producing a photoelectric conversion device according to claim 38, comprising the steps of forming an aluminium layer on the surface of the substrate, anodizing the aluminium layer to form a finely porous alumina layer, and oxidizing at least a part of the substrate to grow a semiconductor acicular crystal through the fine pores of the finely porous alumina layer.
 40. The method of producing a photoelectric conversion device according to any one of claims 35 to 39, wherein a substrate comprising any one of titanium, zinc, and tin in at least a surface thereof is used as the substrate.
 41. The method of producing a photoelectric conversion device according to any one of claims 33 to 35, wherein a substrate having an electrode on a surface thereof is used as the substrate. 